This core has been established to assist PPG member laboratories in the design, production and characterization of transgenic and knockoudknockin mouse strains and to establish, maintain and manipulate neural stem cell and astrocyte cultures. The core will be responsible for all aspects of mouse engineering and will provide scientific advice on issues relating to mouse genetics and biology and to cancer modeling. In addition, the core will harvest wildtype and mutant embryos and adult brains for the purposes of purifying and expanding neural stem cell and astrocyte cultures. The core will also assist investigators of the PPG in the manipulation of these cultures for purposes of gene function evaluation. To better illustrate the utility of this core, we describe two projects that are representative of the core's capacity for servicing the needs of the PPG membership: (1) the generation of a conditional INK4a/ARF mouse and (2) the generation of nestin- and GFAP-driven Cre-ER alleles.